Where Did Robinson Crusoe Go With Friday On Saturday Night?

They went to the corner Malt Shop for a "Sundae".

Robinson Crusoe is the creation of Daniel Defoe(1660-1731). The novel 'Robinson Crusoe' was based on the experiences of Alexander Selkirk who was marooned on an uninhabited island called Mas a Tierra off the coast of Chile.  After Selkirk was rescued he wrote an account of his adventures which was published in 1713.  This inspired Defoe to write the novel.  The man Friday was an invention of Defoe's.  The relationship between Crusoe and Friday was a strange one but of course in those times it could not be expanded upon.  We are left to draw our own conclusions.  As to where they went on a Saturday night that must be left to your imagination.  The phrase you have given comes from an old music hall song that used to be performed by Clinton Ford.